The present invention relates to a direct gasoline injection type spark igniting internal combustion engine with turbocharger and the engine control method thereof, and more particularly to a control mechanism and a control method of an exhaust passage.
Since a direct gasoline injection type spark igniting internal combustion engine directly injects fuel into a cylinder, stratified combustion of collecting and burning fuel near an ignition plug so as to set a lean air fuel ratio as a whole can be conducted. However, in the case of a natural air supply type engine, since an amount of air sucked within the cylinder is small, a range capable of executing a stratified operation is narrow and a sufficient specific fuel consumption improving effect can not be obtained. On the contrary, a system combining a turbocharger and a catalyst (a pre catalyst and a main catalyst) with a conventional direct gasoline injection type spark igniting internal combustion engine is known in Japanese Patent No. 3090536.
In order to increase purification performance at a time of starting an engine, it is general in view of an exhaust countermeasure to additionally provide the pre catalyst assisting the main catalyst near the engine, in addition to the main catalyst placed below a floor of a vehicle body. However, in the case of placing the turbocharger, there is a problem that the turbocharger interferes with the pre catalyst so as to reduce their performances therebetween. As a countermeasure therefor, as shown in Japanese Patent No. 3093536, there is a method of placing valves for switching respective exhaust passages, however, a structure and a control thereof are complex since a number of the valves is increased. Further, in the conventional direct gasoline injection type spark igniting internal combustion engine, there is a problem that an actuation area of the turbocharger does not correspond to the stratified combustion area.
The present invention simplifies a structure and a control by contriving an arrangement of a pre catalyst, a turbine of a turbocharger and a bypass exhaust passage bypassing the turbine so as to set a control valve to one.
Further, the present invention expands a stratified operation area by reducing a capacity of the turbocharger, and shifting the actuation area thereof to a low capacity side so as to coincide it with the stratified combustion area, thereby increasing an amount of air in the stratified area.
In the present invention, an air-fuel ratio (A/F) is shifted to a rich side in an area that the engine rotational speed increases over one half of the maximum rotational speed.